1. Field of the Invention
The present invention relates to control of multiple-motor drivetrains, and more particularly to the control of such a drivetrain to promote even wear within the drivetrain.
2. Description of the Related Art
In control of a vehicle drivetrain having more than one motor, the total torque to be delivered by the drivetrain must be partitioned among the motors of the drivetrain. One way to partition the torque is to simply assign an equal portion of the total torque to each motor (e.g., 50% of the total torque to each motor in a dual-motor drivetrain).
However, where efficiency is an important concern, such as in an electric vehicle, the even split of torque is not the optimal solution. This is true because at a given speed, a motor has an efficiency which is a non-constant function of torque provided by the motor. Because of this, the general case for most operating conditions is that more efficient torque partitioning between the motors in a multiple-motor drivetrain is accomplished by selecting a torque partitioning of other than an even split. Only by chance will an operating condition exist such that an even torque partitioning will be most efficient.
Given that other than an even torque partitioning in a multiple-motor drivetrain is usually the most efficient, a concern is presented. If the same one of the motors is always selected to provide the largest share of the total torque, that motor and the mechanical components driven by it are likely to wear out faster than the other motors and their associated mechanical components. Less than optimal durability of the drivetrain is the likely result.
Therefore, a system which will provide high efficiency as well as high durability of a multiple-motor drivetrain will provide significant advantages.